Up from the ashes

Tree species devastated by blight and insects aren't truly gone until their genetics disappear. Ron Casier, chair of the Canadian Chestnut Council, displayed an American chestnut seedling in Delhi this week that is immune to a killer blight that descended on North America in 1904. A similar genetic rescue of ash trees is underway in southern Ontario.MONTE SONNENBERG / SIMCOE REFORMER

DELHI – Foresters in southern Ontario are not ready to give up on ash trees just yet.

The Forest Gene Conservation Association (FGCA) has asked woodlot owners to report the rare ash trees that survived the passage of the emerald ash borer several years ago.

The goal is to collect seed for the eventual regeneration of ash in southern Ontario and other areas the pest devastated.

“That would count as a best practice,” Norfolk County arborist Adam Biddle said this week at the annual general meeting of the Norfolk Woodlot Owners Association in Delhi.

“Any time you’re faced with the extinction of a tree species, the best thing to do is try to preserve the genetics.”

Working in partnership with the Canadian Forest Service’s National Tree Seed Centre, FGCA has collected seed in southern Ontario from trees that withstood the ash borer onslaught.

Foresters have found that blue ash stood up well while green and black ash showed little tolerance. White ash has come down in the middle, with trees surviving for a few years before succumbing to larval infestations.

Ash researchers have discovered some interesting anomalies in recent months.

They’ve noted that the ash borer had little effect on ash trees planted next to eastern white cedar hedges. They suspect this has something to do with shared root systems and the possibility of transferred biochemical immunity.

Other ash trees are believed to have survived because they were well-attended by woodpeckers. The birds penetrate the bark of trees and eat the insects and larvae beneath.

The association is interested in locating ash survivors in Norfolk and Haldimand counties. Researchers want to preserve as much genetic diversity as possible.

Researchers are especially interested in locating black ash and pumpkin ash. These are likely to be found in wet, swampy areas.

“We did not expect to collect seed or find many trees, but we did,” Melissa Spearing, FGCA’s seed program co-ordinator, said in a recent report to the Norfolk Woodlot Owners Association.

“Observant landowners and managers who had not pre-emptively cut all their natural stands have allowed the rare five in 10,000 green and black ash a chance to show their true colours.”

Seed collected so far has been sent to the National Tree Seed Centre for evaluation. Germination tests will follow. Under climate-controlled conditions, these seeds can be stored for up to 50 years.

This is not the first time science has been used to bring trees back from the brink.

Elm trees are making a comeback nearly 70 years after Dutch elm disease devastated the North American population.

As well, the Canadian Chestnut Council has worked diligently in recent years to collect and combine the genetics of American chestnut trees that are resistant to chestnut blight.

Based on what he has seen to date, Ron Casier of St. Thomas, chair of the chestnut council, is optimistic this majestic tree will eventually return to the Carolinian zone in all its former glory.

“We have very high hopes,” Casier said at the Delhi event. “We have found resistance among our native trees.”

The loss of tree species can have profound ecological impacts. Casier says 11 species – mostly insects – have become extinct since blight attacked the American chestnut population more than 100 years ago.

Ruffed grouse also declined because chestnuts are a key part of the birds’ diet. This in turn caused a drop in the goshawk population – raptors that rely on grouse as a primary prey species.

The emerald ash borer is native to Asia. Foresters suspect it was accidentally introduced to North America in shipping crates and skids about 30 years ago.

Ash borer has since devastated ash stands in the north-east part of the continent. The pest is lethal because it has no natural checks in this part of the world. The hope is the insect disappears once it runs out of ash trees.